The art of sequential manufacturing at successive automated work stations in a rotary path as conventionally practiced involves an integrated rigid multiple station machine and rotatable dial table indexable relative to the respective station locations. Where precision is required between the work operations performed at successive stations, accuracy is normally achieved by precise relative station locations at exact circumferential index increments as well as exact radial location, and workpiece fixtures are rigidly located on the dial table with the exact corresponding circumferential and radial location relative to each of the interrelated stations. Thus, a rigidly integrated composite machine approach involves total dimensional precision and total dimensional interrelationship of all components as well as precise indexing means for the rotatable dial table. In order to achieve both accuracy and rigidity for absorbing the cumulative loads of all working operations the dial table is normally of massive construction involving substantial inertia loads in starting and stopping the table at each index position.
Such conventional approach to multiple station rotary manufacturing systems also involves an integrated common base on which the rigid dimensionally interrelated stations and indexable dial with rigidly located fixtures are mounted. Such approach involves inherent multiple opportunities for tolerance variations--e. g. in station-to-station circumferential dimension; station-to-station location; fixture-to-fixture circumferential dimension; fixture-to-fixture radial dimension; and multiple index locations--all resulting in an inevitable stack up of cumulative tolerance variations. In order to meet demanding requirements for precision in dimensionally interrelated successive operations, highly expensive shop practices are mandated in the assembly of the components--scraping in or shimming component seats, critical adjustments, provisions against warping or strain in set up, elaborate inspection procedures--all add to the costliness of the conventional rigid integrated machine approach.
In addition, a minimum index increment at least adequate for the widest station is required with corresponding index time consumed between stopping one operation and starting the next.
Even where loose pallet, fixture or workpiece individually located at automated stations has been occasionally resorted to, a common indexing approach has been retained imposing constrictions on circumferential spacing of stations and limiting speed of transfer incident to simultaneous indexing.
The closest known prior art relative to applicant's rotary transport system disclosed in a recent search did not involve the problem of accurate interrelation of successive operations or any solution thereto. U.S. Pat. No. 2,507,441 discloses a special purpose glass molding machine employing a pair of separate concentric driven rings for non-synchronous transport of fixturized glass molds with no provision for accurate location or clamping or provision for pallets queuing against each other.
Other patents disclosing various types of rotary apparatus for carrying out work operations include the following: U.S. Pat. Nos. 1,482,687, 2,327,068, 2,447,072, 2,638,201, 2,881,897, 3,180,483, 3,378,907, 3,623,599, 3,647,043, 3,836,003, 4,202,435.